[ntp:questions] Time reset

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Thu Mar 13 08:57:53 UTC 2008

> So its the DISK I/O thats causing loss of ticks ?

My first Red Hat system defaulted to no-DMA for IDE disks.  (Yes,
that was a long time ago.)  With that setup, it was simple to generate
lots of lost timer interrupts: just keep the disk busy doing reads.
(Seeks don't count.  Read consecutive sectors.)

My problem went away when I turned on DMA.

I have a hack that I originally wrote for measuring disk
transfer rates.  I'll dust it off and put it on the wiki
if people think it will be helpful for discussions like this.

It compiles on Linux.  It should be easy to get it to work on
other *nix systems.

These are my opinions, not necessarily my employer's.  I hate spam.

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